Grain-oriented electrical steel sheet, and manufacturing method therefor

Abstract

A method for manufacturing a grain-oriented electrical steel sheet, according to one embodiment of the present invention, comprises the steps of: hot rolling a slab so as to manufacture a hot rolled sheet, the slab comprising, by wt %, 2.5-4.0% of Si, 0.03-0.09% of C, 0.015-0.040% of Al, 0.04-0.15% of Mn, 0.01% or less of S (excluding 0%), 0.002-0.012% of N, 0.01-0.05% of Sb, 0.03-0.1% of Sn, 0.05-0.2% of Cr and the balance of Fe and inevitable impurities; cold rolling the hot rolled sheet so as to manufacture a cold rolled sheet; and performing secondary recrystallization annealing on the steel sheet having undergone primary recrystallization annealing.

1 . A method for manufacturing a grain-oriented electrical steel sheet, the method comprising:
 manufacturing a hot-rolled sheet by hot rolling a slab containing, by wt %, 2.5 to 4.0% of Si, 0.03 to 0.09% of C, 0.015 to 0.040% of Al, 0.04 to 0.15% of Mn, 0.01% or less (excluding 0%) of S, 0.002 to 0.012% of N, 0.01 to 0.05% of Sb, 0.03 to 0.1% of Sn, 0.05 to 0.2% of Cr, and a balance of Fe and inevitable impurities;   manufacturing a cold-rolled sheet by cold rolling the hot-rolled sheet;   subjecting the cold-rolled sheet to primary recrystallization annealing; and   subjecting the steel sheet subjected to the primary recrystallization annealing to secondary recrystallization annealing,   wherein the subjecting of the cold-rolled sheet to the primary recrystallization annealing includes:   measuring the amount of nitriding of the steel sheet after the primary recrystallization annealing; and   controlling an exposure time to nitriding gas during the primary recrystallization annealing according to the measured amount of nitriding, and   the amount of nitriding and the exposure time to the nitriding gas satisfy the following Expression 1:   [Expression 1]   Δ[N]/Δt≥0.025   (in Expression 1, Δ[N] represents the amount (wt %) of nitriding of the steel sheet after the primary recrystallization annealing, and Δt represents the exposure time (minutes) to the nitriding gas).   
     
     
         2 . The method of  claim 1 , wherein:
 the slab further contains one or more of Ti and V in an amount of 0.002 to 0.01 wt % alone or as a mixture.   
     
     
         3 . The method of  claim 1 , wherein:
 the slab satisfies the following Expression 2:   [Expression 2]   [Sb]≤[Cr]≤[Sb]+2×[Sn]   (in Expression 2, [Sb], [Cr], and [Sn] represent contents (wt %) of Sb, Cr, and Sn in the slab, respectively).   
     
     
         4 . The method of  claim 1 , wherein:
 the subjecting of the cold-rolled sheet to the primary recrystallization annealing is performed in an atmosphere having an oxidation capacity (PH 2 O/PH 2 ) of 0.5 to 0.8.   
     
     
         5 . The method of  claim 1 , wherein:
 the subjecting of the cold-rolled sheet to the primary recrystallization annealing is performed at a temperature of 800 to 900° C.   
     
     
         6 . The method of  claim 1 , wherein:
 after the subjecting of the cold-rolled sheet to the primary recrystallization annealing, an oxide layer having an average thickness of 1.6 to 3.2 μm is present on a surface of the steel sheet.   
     
     
         7 . The method of  claim 1 , wherein:
 after the subjecting of the cold-rolled sheet to the primary recrystallization annealing, the amount of nitriding of the steel sheet is 0.02 to 0.04 wt %.   
     
     
         8 . A grain-oriented electrical steel sheet comprising:
 a base material containing, by wt %, 2.5 to 4.0% of Si, 0.005% or less (excluding 0%) of C, 0.015 to 0.040% of Al, 0.04 to 0.15% of Mn, 0.01% or less (excluding 0%) of S, 0.005% or less (excluding 0%) of N, 0.01 to 0.05% of Sb, 0.03 to 0.1% of Sn, 0.05 to 0.2% of Cr, and a balance of Fe and inevitable impurities; and   a metal oxide layer located on the base material,   wherein a maximum emission intensity ratio [I(Ti)/I(Mg)] of the metal oxide layer is 0.05 or more.   
     
     
         9 . The grain-oriented electrical steel sheet of  claim 8 , wherein:
 the base material further contains one or more of Ti and V in an amount of 0.002 to 0.01 wt % alone or as a mixture.   
     
     
         10 . The grain-oriented electrical steel sheet of  claim 8 , wherein:
 the base material satisfies the following Expression 2:   [Expression 2]   [Sb]≤[Cr]≤[Sb]+2×[Sn]   (in Expression 2, [Sb], [Cr], and [Sn] represent contents (wt %) of Sb, Cr, and Sn in the base material, respectively).   
     
     
         11 . The grain-oriented electrical steel sheet of  claim 8 , wherein:
 whiteness of the grain-oriented electrical steel sheet is 43 to 51.   
     
     
         12 . The grain-oriented electrical steel sheet of  claim 8 , wherein:
 the metal oxide layer contains 0.003 wt % or more of Ti.   
     
     
         13 . The grain-oriented electrical steel sheet of  claim 8 , further comprising an insulating coating layer located on the metal oxide layer,
 wherein a ratio of the sum of thicknesses of the metal oxide layer and the insulating coating layer to the total thickness of the grain-oriented electrical steel sheet is 0.03 or less.